Hepatocyte growth factor (HGF), also known as scatter factor, is a multi-functional growth factor that enhances transformation and tumor development by inducing mitogenesis and cell motility. Further, HGF promotes metastasis by stimulating cell motility and invasion through various signaling pathways. In order to produce cellular effects, HGF must bind to its receptor, c-Met, a receptor tyrosine kinase. c-Met, a widely expressed heterodimeric protein comprising of a 50 kilodalton (kDa) a-subunit and a 145 kDa alpha-subunit (Maggiora et al., J. Cell Physiol., 173:183-186, 1997), is overexpressed in a significant percentage of human cancers and is amplified during the transition between primary tumors and metastasis. The various cancers in which c-Met overexpression is implicated include, but are not limited to, gastric adenocarcinoma, renal cancer, small cell lung carcinoma, colorectal cancer, prostate cancer, brain cancer, liver cancer, pancreatic cancer, and breast cancer. c-Met is also implicated in atherosclerosis and lung fibrosis.
Accordingly, there is a great need to develop compounds useful as inhibitors of c-Met protein kinase receptor. In particular, preferred compounds should have high affinity to the c-Met receptor and show functional activity as antagonists, while showing little affinity for other kinase receptors or for targets known to be associated with adverse effects.